Such a tensioning device is generally utilized to apply a constant tension to the means of traction within a given range and/or to modify locally the circuit produced by the latter.
Once installed in the traction circuit, the means of traction is driven by at least one engine element, in particular by a crankshaft of the internal combustion engine, and drives at least one element, to which it is connected, and which must be set in motion, in particular a compressor or a generator.
The connections between, on the one hand, the means of traction and the engine element and, on the other hand, the means of traction and the driven element are made by means of pulleys installed on these elements. The means of traction is placed under sufficient tension by being connected to the tensioning device in the traction circuit in order to prevent any slipping on the pulleys and to permit its optimized functioning.
The customary method of installation of a traction element in a traction circuit consists of:                installation of the pulleys connected to the engine elements and the elements to be driven, and at least one tensioning device,        followed by installation of the means of traction around the pulleys and installation of the tensioning device,        and, finally, tensioning of the means of traction by adjustment of the tensioning device.        
For this final stage of the method, the utilization of a spring or of a lever arm provided in the tensioning device, for example the device described in US patent application 2008/0207367 A1, is already familiar.
However, such devices require numerous supplementary parts in order to achieve this function, involving a high cost accompanied by a longer installation time for the tensioning device.
Furthermore, the utilization of a spring or of a lever arm in order to ensure tensioning of a means of traction to a desired value causes significant congestion at the level of the traction circuit. For this reason, it cannot be utilized for certain applications of the tensioning device.
The present invention sets out to address these problems in particular by proposing a new tensioning device with a reduced number of parts and with reduced congestion, and by simplifying the method of installation of the means of traction.